Aerial bomb control system



Aug. 3, 1948. J. H. HAMMOND, JR

AERIAL BOMB CONTROL SYSTEM 4 Sheets-Sheet 1 Filed Sept. 19, 1942 INVENTOR JO H N HAYS HAMM 0ND,JR

Aug. 3, 1948. J. H. HAMMOND, JR

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AERIAL BOMB CONTROL SYSTEM Filed Sept. 19, 1942 4 Sheets-Sheet 5 muiuuum QDL-UMJUW LIME-kw INVENTOR JOHN HAYS HAMMOND, JR.

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AERIAL BOMB CONTROL SYSTEM Filed Sept 19, 1942 4 Sheets-Sheet 4 RECEIVER NVENTOR RADIO Patented Aug. 3, 1948 AERIAL BOMB CONTROL SYSTEM John Hays Hammond, In, Gloucester, Mass.,'as- Signor to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application September 19, 1942, Serial No. 458,938

4 Claims. 1

This invention relates to the radio-dynamic control of aerial bombs and more particularly to a radio control system of the above type which cannot be interfered with from the ground.

The invention provides means for controlling the direction of descent of a bomb in two planes perpendicular to each other so that the bomb may be guided by remote control in any desired direction.

The invention also consists in certain new and original features of construction and combinations of parts hereinafter set forth and claimed.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organization may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part thereof, in which Figure l is a diagrammatic illustration of a portion of an airplane, including the bomb bay;

Fi ure 1a is a perspective view of a bomb as released from the airplane of Figure 1;

Figure 2 is a schematic diagram of the trans- Y mitting circuits on the airplane;

Figure 3 is a schematic diagram of the receiving circuits located in the bomb; and

Figure 4 is a partial section through a bomb illustrating diagrammatically the control apparatus for steering the bomb during its descent.

Referring to the accompanying drawings and more particularly to Figures 1 and 1a the airplane II is shown as provided with the usual bomb bay l2 behind which is an opening I3 in which is located the antenna system I I of the transmitter to be described. This antenna system is mounted on suitable means, shown as gimbal rings I5, so that it may be pointed in any desired direction. A sighting means, shown as a telescope I6, is attached to the antenna system I4 to facilitate following the bomb in its descent. The antenna system M is of the type adapted to radiate polarized, directional, short waves in the form of a beam. In the embodiment shown this system comprises a dipole radiator Isa mounted in a reflector system Mb. It is to be understood, however, that any standard type of directional beam short wave radiator may be used.

As shown in Fig. 1a. the bomb I1 is provided with the usual fins Ill in which are located two sets of rudders I9 and 2| whose axes of rotation are at right angles to each other. Mounted on the ends of the fins I8 are two directional receiving antennas 22 and 23 the axes of which are located in planes at right angles to each other, and preferably in the planes of the axes of the rudders I9 and 2I. The antennae 22 and 23 are shown as similar in construction to the antenna it and are of the type suited to receive polarized short waves from a given direction only, i. e. from above. The antennae are shown as comprising wave receiving members 220. and 23a and directional members 221) and 23b which correspond to the reflector Mb. The directional members are suited to make the receiving elements receptive to signals received from above and to shield the receiving members from waves propagated from the ground and from horizontal waves so that possibility of interference with the control beam transmitted from the airplane is eliminated.

Figure 2 depicts the transmitter which is installed on the airplane I I. This transmitter is generally of conventional design and only so much thereof is set forth herein as is necessary to an understanding of the present invention. The transmitter is shown as comprising a master radio frequency oscillator, a modulated power amplifier connected to feed the antenna I4, an amplitude modulator, and a control frequency generator.

The master radio oscillator comprises a pentode oscillator tube II I the control grid I Hg of which is connected to a frequency determining circuit H3. The inductor H31 of the frequency determining circuit H3 is tapped and connected to the cathode II'Ic to supply the necessary feed back from the plate circuit. The second or screen grid I I Is is positively biased and the plate circuit includes atuned circuit H4, which is tuned to double the frequency of the oscillator and is energized from the harmonic having double the frequency of the grid circuit of pentode III.

The modulated power amplifier includes a pentode H5 of the self biased type, the cathode H5c of which is connected thru a bleeder resistor III to the positive terminal of a battery H8. The cathode l I5c of the pentode H5 is also connected to one end of a keying resistor H9 the other end of which is connected to the arm of a key 38. The resistor H9 varies the bias of the tube H5 to render the power amplifier operative only when the key 38 is closed. The first control grid 59 is energized from the buffer doubler circuit H4.

The plate I I512 of the tube I I5 is connected thru an output tank circuit I24, filter choke I25 and a secondary winding I26 of a transformer I52 to the positive side of the plate battery I21. Radio frequency bypass condensers I28 are connected across both ends of the choke I25 to ground. The second grid I |s of the tube I I5 is connected thru a radio frequency choke I29 and a secondary I39 of the transformer I52 to the positive side of the battery H8. Radio frequency bypass condensers I3! are connected across both ends of the choke I29 to ground. The output tank circuit |24 is inductively coupled to a coil I32 feeding a transmission line |33 to the radiating doublet or dipole I4.

The control frequency generator includes a self biased triode I35. The plate circuit is connected thru oscillator coil I31 to the movable arms of the keys 30-33. Between the front contacts of the keys 30-33 and the positive sideof a plate battery I33 are connected resistors 34-31, which are adjusted so that the amount .of modulation is the same for all channels. A bypass condenser I39 is connected across the movable arms of the keys 30-33 to the positive side of the battery I38. The back contacts of the keys 30-33 are connected thru trimmer'condensers |4l of different capacities to the plate I351) of the tube I35. The main oscillatory condenser I 45 is connected across the oscillatory coil I31.

A secondary coil 140 is coupled to oscillator coil I31. The coil M6115 connected to feed modulator tubes. I41 and I48. The center tap |4Ba is connected to ground and a second tap I452) suitably chosen on the proper side of center is connected to the grid |35g of the tube I35.

Each of the keys 30-33 is connected mechanically to the key 38 as by a rod 33a which is pushed upwardly by the-respective keys 3|].to 33 in such a manner that when any one of the keys 30-33 is closed the key 39 will also be closed.

In the operation of the transmitter of Figure 2 a radio frequency is generated by the master radio oscillator and is impressed on the power amplifier. When the key 38. is open the radio frequency is not radiated by the antenna |4, however, due to the high positive bias on the cathode of the amplifier tube II5, which prevents its operation. When the key 30 is depressed an "A control frequency isgenerated by the control frequency generator'from which it passes through the modulator and is impressed upon themodue lated power amplifier. At thesame time the key 38is closed reducing thepositive bias on the tube M5 to normal and unblocking the same, whereupon the radio frequency is modulated in a well known manner. The modulated Wave is then radiated from the directional antenna I4 in the form of a plane polarized wave.

When the keys 3|, 32 and, 33 are individually depressed B, C and D control frequencies respectively are generated and modulate theradio frequency generated by the master radio oscillator accordingly. In this way when any one of the keys 30-33 is depressed a plane polarized wave is radiated from the antenna 'I4, this wave being modulated at a different predetermined frequency for each key.

In Fig. 3 is depicted thereceiving circuits installed in the bomb I1. These circuits comprise a radio receiver of the superheterodyne type which is connected to the directiveantenna system 22-23 and includes a final detector and an automatic volume control. The output of the final detector is connected to a selector system including a first selector, a limiter and a second selector which is connected through two transformers 49 and 50 to a final selector, comprising four tubes 52-55. The output circuits of the tubes 52-55 are connected through four trans- 4 formers 56-59 respectively to four diodes 5| to 64, which form a thermal type A. C.-D. C. converter system. The four diodes 6| to 64 are connected to the grids 65g-68g of four power tubes 65-88 the output circuits of which include the windings of four solenoids 1 |14.

The leads from the antennas 22 and 23 are connected inseries and the transmission line from the antenna 23 is a quarter wave length longer than that for the antenna 22. The superheterodyne receiver is of standard construction and includes the usual R. F. circuits, first detector and'I. F; circuits, indicated by the rectangle 4| terminated by-an I. F. output transformer 15 and a. diode 16 which constitutes a second detector and may be provided with an automatic volume control circuit which includes a diode 11, a condenser 18 and resistors 19 and 80. If desired the selectivity may be increased by including a resistor in series with the plate 151) of the diode 16.

The; first selector includes a transformer I04 the-secondary of which is connected to the grids 41g, 48g of the second selector tubes 41 and 48 in p rallel.

The plates 6|p-64p of the diodes Iii-64 are connected, to the junction of batteries I01 and I00. The grids 65g-68g of the power tubes 55-60 are connected through resistors III and H2 to the negative side of a battery I05. The cathode-filaments 050-680 of the power tubes 65-38;.are shown as supplied from a battery I00.

The; receiver isresponsive to energy radiated froimthe transmitter of Fig. 2 and picked up by one-of thetw-o antennas 22 and 23, which are mountedat right angles to each other in a plane perpendicular; tothe direction of radiation from the transmitter. The transmission line from the a fll fin-na- 23i is aquarter wave length longer than that for the antenna 2-2; so that at the receiver the signals' due to the two antennas are quadrature related in phase, provided they are in phase-attheantennae. That is, if is the angle ofthe electric vector of the incident plane polarized wave-with therod of antenna 23 then for a wave Asinwt impressed on the system, the voltages picked up, at; the two antennas will be A sin wt cos s and Aisin'wt Si11 respectively. Assurning no loss ,of voltage in transmission over the line to the receiver 4|, there will be a phase lag in; waves received byantenna 23 of a quarter wave length or electrical degrees with respect to waves; received by antenna 22, whereby the voltage'er at, the receiver terminals will be er -A cos sin [(wt-a-l] A sin sin [(wi-a) -90] Therefore the strength of the signal at the receiver is independent of'the angle of polarization. This is of importance if the angle is a slow variable, and it isdesired to maintain constancy of'signal;

The intermediate-frequency energy due to the signal; which may be modulated by a control frequency, is impressed through the secondary of the transformer 15 on tothe final detector 16 resulting in a pulsating current thru the circuit including the primary of the transformer I04 of the first selector-44. The rate of these pulsations corresponds tothe rate of the modulations. The transformer of the first selector is so arranged that substantially the same transmission is available for all the possible control frequencies.

The signal from the transformer of the first selector, which is broadly responsive to all the control frequencies A, B, C and D, is impressed through the limiter on the grids 41g, 48g of the tubes 41 and 48 of the second selector. In this way the voltage impressed on the grids 41g, 48g is independent of the strength of the signal over a considerable range of signal strengths. The construction of the limiter 45 and its operation are well known, being shown, for example, in U. S. Patent 1,560,206 to E. L. Chaifee. This type of limiter produces a square top or clipped Wave from a sine wave. This device is an aid to the automatic volume control in making certain that the signals will be the same regardless of which transmitter key is used and regardless of the signal strengths.

The tubes 4'! and 4% feed the transformers 49 and 50 respectively, which are each selective to the transmission of two of the possible control frequencies. Thus, for example, the transformer 49 may be selective to the frequencies A and B produced when the keys 30 and 3| are closed and the transformer 50 may be selective to the frequencies C and D produced when the keys 3'2 and 33 are closed. The transmission through the transformers 69 and 50 may be of the doublehumped nature.

The output of the transformer 49 is connected in push-pull to the input circuits of tubes 52 and 53 and the output of the transformer 50 is connected in push-pull to the input circuits of tubes ISA-and 55. The outputs of the tubes 52-55 are connected to transformers NS-59 respectively which are selective respectively to the signals produced when the individual keys 30-33 are closed. The energy from the transformers 55-59 is supplied to heat the filaments Elf-454 of the diodes iii-'64, respectively, which become conductive from plate to filament in accordance with the well known Edison effect.

Take, for example, the top selective circuit starting with transformer 55. The plate Blp of the diode BI is made positive with respect to its filament 6|) by being connected to the junction of the batteries I01 and I08, the grid 65g of the tube 65 is biased in the vicinity of or beyond cut oil by the battery I05 and the solenoid H is connected in the plate lead of the tube 65 from the highest potential point on the battery system I05-l08. When the filament 6 If of the diode BI is sufficiently heated due to the signal energy received when the key 30 is closed the diode 6|. becomes conductive in the direction of the arrow, producing a current flow in the resistor H2 in the direction of the arrow, which makes the grid 65g of the tube 65 less negative and increases the D. C. current in the solenoid ll. Resistor Ill limits the voltage that is impressed upon the grid of the tube 65 when the grid 659 current starts to flow due to the bias becoming zero.

It is thus seen that the signal current produced by closing the key 30 causes the filament 6| of the diode 6| to become heated, which in turn causes the tube 65 to pass plate current to energize the solenoid 1 I. In a like manner when the key 3|, 32 and 33 are closed the corresponding solenoids 12, i3 and 14 will be energized.

While the usual type of rectifiers may be used for A. C.-D. C. conversion, the circuits would be much more complex to produce the desirable characteristics of high threshold of operation. Preferably the range of control frequencies is made less than one octave to prevent harmonics of one control frequency from coinciding with the fundamental of another control frequency.

In Figure 4 is shown the apparatus for controlling the rudders i9 and 2| in response to the cnergization of the four solenoids ll-I4 illustrated in Figure 3. The two sets of rudders l9 and 2| are connected by links 8| to piston rods 82 which are attached to pistons 83 which reciprocate in two cylinders 84 and 85. Balanced compression springs 86 are provided for normally holding the pistons 83 and therefore the rudders i9 and Z! in a central position.

The pistons 83 are actuated by air under pressure which is supplied from a tank 81. This tank is shown as being connected by a pipe 88 to a funnel shaped opening 89 in the nose of the bomb IT. A flask (not shown) containing air under pressure could also be used as a source of compressed air if desired. The tank 81 is con nected to the cylinders 84 and 85 by means of conduits 3! and the supply of air to the interior of the cylinders 84 and 85 is controlled by two piston valves 92 and 93 respectively. The valve 92 is operated in opposite directions by means of the solenoids H and 12 and the valve 93 is operated in opposite directions by means of the solenoids 73 and M. Balanced compression springs 34 are provided to maintain the valves 92 and 93 in a central position when the solenoids 'H14 are deenergized.

The solenoids lb-l4 are connected to the radio receiver 35 the circuits of which are shown in Figure 3. The radio receiver 95 is mounted upon a transverse bulkhead 96 which divides the bomb into two compartments 9'! and 98. The former contains the control apparatus just described and is provided with two vents 99. The latter is filled with a high explosive, such for example as TNT and is provided with the usual fuses, not shown, for detonating the explosive charge when the bomb reaches its target.

In the operation of the control mechanism shown in Figure 4, the descent of the bomb I1 causes air to enter the opening 89 and to flow thru the pipe 88 to the tank 81. A considerable air pressure will be built up within this tank due to the rapid descent of the bomb. When one of the solenoids, for example, solenoid 13, is energized by the transmission of the C frequency, the valve 93 will be moved upward and will allow air under pressure from the tank 81 to enter the upper end of the cylinder 85. This will cause the piston 83 to move downward which, by means of the rod 82 and link 8|, will cause a rotation of the rudder 2| in a clockwise direction. This will cause the bomb to be deviated to the right.

When the transmission of the 0 frequency ceases the solenoid 13 will be deenergized and the valve 93 Will be returned to its central position under the action of the springs 94. The piston 83 together with the rudder 2| will also be returned to a central position under the action of the springs 86. The bomb will then continue on its new course slightly to the right of its former course, the amount of deflection being determined by the length of the C frequency impulse.

When the solenoid M is energized by the transmission of the D frequency the opposite action will take place and the rudder 2| will be rotated in a counterclockwise direction to deflect the bomb to the left. B energizing the solenoids H or 12 by the A or B frequencies the bomb I! will be deflected in a plane at right angles to the plane of the drawing.

It is thus seen that a control system for aerial bombs has been developed which permits the steering of the bombs in four directions at 90 degrees to each other by the depressing of a selected one of four keys located on the plane. In this way the bomb may be caused to deviate from its original course the amount of deviation depending on the length of time that the control key is depressed.

With the directional antennas mounted on the tail of the bomb only radiations from above will be received so that it would be impossible for anyone on the ground to interfere or control the bomb even though they were able to ascertain the frequency and modulation of the control wave. In order to eliminate any possible interference from broadcast type of transmitters the transmitter on the plane may be arranged to use supersonic modulation frequencies and the radio carrier wave may be artificially wobbled or frequency modulated to reduce interference from continuous wave transmitters. This control system relies chiefly for selectivity on the directive antenna efiect, on the limited duration of the control impulses, on the receiver limiter and volume control action and upon the high threshold of signal for the operation of the solenoids.

For high altitude bombing the bombs may be released from one or more airplanes of a flight and controlled by a following plane which is in a position to observe their flight.

Although only a few of the various forms in which this invention may be embodied have been shown herein, it is to be understood that the invention is not limited to any specific construction but may be embodied in various forms without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

1. A radio receiving means responsive selectively to a lurality of different signals, comprising a radio receiver having a final detector connected to detect any of said signals and a volume .control means connected to render the output of said detector substantially independent of signal strength, a first selector circuit broadly tuned to respond to all of said signals, a second selector fed by said first selector circuit and having a pair of tuned circuits each tuned to receive a different set of said signals, a final selector circuit including a plurality of circuits tuned individually to the-respective signals and each vfed by the second selector circuit which is tuned to pass the respective signal, and a control circuit. actuated in response to the signals from each of said final selector circuits.

2. A receiving system in accordance with claim 1 in which a limiting circuit is included between said first selector and said second selector so as to make the response of said second selector substantially independent of input signal strength.

3. The invention set forth in claim 1 in which the control circuits comprise solenoids, power tubes feeding said solenoids and means feeding said power tubes respectively from the respective circuits of the final selector.

4. A signal receivin system as set forth in claim 1 comprising thermionic rectifiers fed by the respective circuits of said final selector to pass current only when the energization there- 'of exceeds a predetermined value, power tubes REFERENCES CITED The following references are of record in the his of this patent:

UNITED STATES PATENTS Number Name Date 1,249,274 Chandler Dec. 4, 1917 1,597,416 Mirick Aug. 24, 1926 1,805,591 Ohl May 19, 1931 1,952,326 Ludenia Mar. 27, 1934 2,131,042 Halstead Sept. 27, 1938 2,165,800 Koch July 11, 1939 2,209,982 Kirkwood Aug. .6, 1940 2,245,347 Koch 1- June10, 1941 2,254,739 Grayson 1 Sept. ,2, 1941 2,272,839 Hammond Feb. 10, 1942 2,273,911 Usselman Feb. 24, 1942 2,282,102 Tunick May .5, 1942 2,368,778 Purington Feb. 6, 1945 2,396,091 De Bey Mar. 5, 1946 2,397,475 Dinga Apr. 2, 1946 2,408,472 Moynihan Oct. 1, 1946 FOREIGN PATENIS Number Country Date 524,876 Great Britain Aug. 16, 1940 

